A radar apparatus is known which detects the target object by transmitting the radio wave in the forward direction of the vehicle and receiving the reflected wave of the transmitted radio wave generated by the reflection on the target object, and the detection result is used for preventing a collision with the target object such as a preceding vehicle, a oncoming vehicle, a wall, etc., or controlling the distance between the host vehicle and the preceding vehicle (see Patent Document 1, for example). According to the disclosed radar apparatus, reflection points are detected in plural directions. The reflection points, which are estimated to belong to the same target object, are classified into the same group. The lines defining the area of the target object are extracted based on an arrangement of the reflection points of the group. Therefore, according to the radar apparatus, the area of the target object can be detected.
[Patent Document 1] Japanese Laid-open Patent Publication No. 2000-206241